// No.179 塗り分け
#include <iostream>
#include <vector>
using namespace std;

int main() {
    int H, W;
    cin >> H >> W;
    vector<vector<char>> S(H, vector<char>(W));
    for (int i = 0; i < H; ++i) {
        for (int j = 0; j < W; ++j) {
            cin >> S[i][j];
        }
    }
    vector<vector<bool>> used(H, vector<bool>(W, false));
    for (int dy = -H + 1; dy < H; ++dy) {
        for (int dx = -W + 1; dx < W; ++dx) {
            if (dy == 0 && dx == 0) continue;
            used.assign(H, vector<bool>(W, false));
            int painted = 0;
            bool ok = false;
            for (int xy = 0; xy < H * W; ++xy) {
                int y = xy / W, x = xy % W;
                if (S[y][x] == '.') continue;
                if (used[y][x]) continue;
                if (y + dy < 0 || y + dy >= H || x + dx < 0 || x + dx >= W) {
                    ok = false;
                    break;
                }
                if (S[y + dy][x + dx] == '.') {
                    ok = false;
                    break;
                }
                if (used[y + dy][x + dx]) {
                    ok = false;
                    break;
                }
                ok = true;
                used[y][x] = used[y + dy][x + dx] = true;
            }

            if (ok) {
                cout << "YES" << endl;
                return 0;
            }
        }
    }
    cout << "NO" << endl;
}